1. Field of the Disclosure
This disclosure relates generally to three-way catalyst (TWC) systems and, more particularly, to the TWC property of synergized PGM catalysts.
2. Background Information
Many modern functional materials are made of multi-phase entities in which cooperative behavior between different components is required to obtain optimal performance. Typical situations of cooperative behavior are modern TWC systems utilized in vehicle exhausts to reduce exhaust gas emissions. TWC systems convert the three main pollutants in vehicle exhaust, carbon monoxide (CO), unburnt hydrocarbons (HC) and oxides of nitrogen (NOx), to H2O, CO2 and nitrogen. Typical TWC systems include a support of alumina upon which both platinum group metals (PGM) material and promoting oxides are deposited. Key to the desired catalytic conversions is the structure-reactivity interplay between the promoting oxide and the PGM metals, in particular regarding the storage/release of oxygen under process conditions.
Current TWCs are exposed to high operation temperatures due to the use of closed-loop coupled catalysts near the engine. Additionally, TWC's demand for PGM and rare earth metals continues to increase due to their efficiency in removing pollutants from internal combustion engine exhausts, placing at the same time a strain on the supply of PGM metals, which drives up their cost and the cost of catalysts applications.
As PGM catalysts usually work close to stoichiometric condition, it is desirable to increase their activity under lean condition close to stoichiometric condition. Under lean condition NOx conversion may be increased by synergizing PGM. This synergistic effect improves fuel consumption and provides fuel economy. For the foregoing reasons, there is a need for combined catalyst systems that may exhibit optimal synergistic behavior yielding enhanced activity and performance and up to the theoretical limit in real catalysts.